Electrocardiograph (ECG) signals include signals that are measured from leads external to the heart, typically that are attached to the body surface (BS), as well as those from intra-cardiac (IC) electrodes contacting the heart. The signals are inherently relatively low level signals and have relatively high impedance sources. Because of this and other environmental factors, in medical procedures such as mapping the electrical activity of the heart, the measurements are typically relatively noisy. A system to increase the accuracy of the measurements, and to reduce the effect of the noise on the measurements would be beneficial.